Poliomyelitis or Polio is an acute viral disease caused by poliovirus, from the picornavirus family, which can damage the digestive tract and the nervous system, leading to flaccid paralysis.1
The global importance of polio is underlined by the fact that a day (October 24) is set aside by the World Health Organization (WHO) known as World Polio day.2
Polio has some peculiar characteristics that highlight its global health importance. First, it is mainly a disease of children under five years, although older adults can be infected by the virus. It is very acute and spreads very fast through the fecal-oral route, often leading to debilitating paralysis, which handicaps victims and reduces quality of life and even death in some cases. Even more interesting is that till date, polio has no known cure, but could be preventable, mainly by vaccine and reduction of risk factors for contacting the disease.3
The discovery and production of polio vaccines-inactivated polio vaccine (IPV) and oral polio vaccine (OPV) in the 1950s and subsequent massive global anti-polio immunization campaigns through the Global Polio Eradication Initiative (GPEI) changed the picture and infection rates plummeted rapidly, leading to the declaration by the WHO in 1988 that polio would be eradicated worldwide by the year 2000.4,5
Two decades after the WHO polio eradication declaration, the overall picture continued to improve; incidence rates worldwide dropped significantly from 350, 000 in 1988 to 866 cases in 2008, which represent a 99% decline in infection rate, and polio endemic countries from 125 in 1988 to only 4 as at present.4
One of these four countries is Nigeria, which remains the only polio endemic country in Africa that has never been able to achieve interruption of wild polio virus transmission. Hence, Nigeria is considered worldwide as a reservoir of polio virus and many new cases continue to be reported yearly.6,7
Presently, Nigeria accounts for almost 60% of earth's wild polio transmission incidences, thus remaining the biggest threat to the realization of a polio-free earth by the WHO.8,9
Another complication caused by the Nigerian situation is that there have been documented cases of transmission of the poliovirus from Nigeria to other countries, both in Sub-Saharan Africa, and other parts of the world, causing a re-infection in populations already declared polio free; and so far between 18 and 20 countries have been re-infected by strains genetically linked to original strain from some parts of Nigeria;10,11
polio strains from Nigeria were responsible for 80% of worldwide polio cases at the time of the polio vaccine boycott.11
One challenge in the fight against polio is the dearth of empirical literature, and paucity of data that accurately quantify the dynamics of this infectious disease. Nevertheless, a lot has been gleaned from available though scanty literature from Nigeria, Africa, and rest of the world that helps to describe the problem of polio in Nigeria. From some of these literature, it is now known that there are some clear disparities in incidence of polio in Nigeria, as well as the utilization of immunization and vaccination services in the fight against polio in earth's most populous black nation.
There is a geographical disparity in incidence rates of polio across the Nigerian State, and it is split between the Southern, predominantly Christian population, and the Northern, predominantly Muslim population.8,12
This North-South disparity (Figures , ) is so evident that when writing about polio in Nigeria, most of the available literature would only discuss in terms of Northern Nigeria, as the South is generally considered free , although the problem of re-infection of southern population remains often obliterate this clear divide.9
This disparity exists, not only in the rate of disease incidence, but also the utilization of globally recommended and accepted preventive care: immunization.12
Figure 1 Confirmed cases of wild poliovirus in Nigeria and surrounding African countries in 20039
Figure 2 Confirmed cases of wild poliovirus in Nigeria and surrounding African countries in 20029
This geographic disparity as a result can be attributed to a combination of factors; largely determinants of health which are so convoluted that they are difficult to discuss exclusive of each other. They include in this case environmental exposures, social circumstances, shortfalls in medical care and health behavior. Again, this paper is painfully limited by the paucity of data describing these health determinants in Nigeria as it affects polio, but some direct and some inferential evidence exist to show how these determinants drive the cause of polio eradication in Nigeria.